Multiple cannula image guided tool for image guided procedures

ABSTRACT

Apparatus and methods are disclosed for use within an image-guided surgical navigation system for facilitating the combined positioning and orientation of multiple surgical implements. A tool guide having multiple cannulas is tracked by a surgical navigation system in real time. Position data of the tool guide is registered and combined with pre-acquired images by the navigation computer. Concurrent graphical representations of the plurality of cannulas are superimposed over the images and displayed. The display allows the surgeon to place the tool guide into the patient&#39;s body and position and orient the plurality of cannulas which are then used to place each of the implements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent Ser. No. 09/795,126,filed on Mar. 1, 2001, now U.S. Pat. No. 6,725,080 which claims thebenefit of U.S. Provisional Ser. No. 60/186,200, filed Mar. 1, 2000. Thedisclosures of the above applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention is directed generally to image-guided medicalprocedures, and more particularly, to instrumentation for the optimalplacement of multiple surgical implements using image-based surgicalguided navigation systems.

2. Description of the Related Art

Many surgical procedures include a surgeon placing multiple implementswithin a patient's body. Some of these procedures dictate implementplacement in a specific geometry to maximize the effectiveness of thetreatment. Certain factors, such as the characteristics of the patient'sanatomy, can also influence the desired relative placement of themultiple implements. Some procedures place the implements at a specifiedangle relative to each other, while others may use a parallelarrangement. One such procedure which utilizes a parallel configurationis the fixation of a femoral neck fracture. Typically, this type offracture is stabilized utilizing three parallel cannulated screws. Eachscrew is placed perpendicularly to the fracture site and in such amanner that the distance between each screw is equal, thus forming anequilateral triangle. Parallel placement of the screws is desired sothat the bones are properly pulled together. If the screws are notplaced in such a parallel manner, shearing forces at the fracture sitecan prevent proper healing. Furthermore, the triangular screwarrangement increases the stability of the fracture fixation andprevents rotation between the bone fragments. Studies have suggestedthat three screws are an optimal number since additional implementsprovide no strength advantage and additional screw penetration increasesrisk. Femoral neck fracture stabilization using this method can beperformed percutaneously while the patient is under regional anesthesia,thus reducing risk associated with more invasive procedures.

Traditional techniques to accurately position and orient implements haveincluded the use of x-ray images to localize the position of theimplement tool guide. Through the continuous acquisition of x-ray imagesduring the medical procedure, real-time placement of the tool guiderelative to the patient's anatomy can be displayed. More recently,fluoroscopically-based surgical navigation systems have been employedfor tool guide positioning by tracking the tool and superimposing itsrepresentation onto pre-acquired images without requiring x-rays to becontinually taken during the actual surgical procedure.

Current practice for multiple implement placement utilizing image-basedsurgical navigation systems typically employs tracked guides whichcontain a single cannula. As used herein, the term cannula refers to atubular member having at least one hollow channel (i.e., lumen), forinsertion in and/or placement adjacent to a patient's body. Such aninstrument could be used to place implements in and/or adjacent to apatient by positioning the cannula in the region of interest, and thenplacing the implement in the region by means of the channel. As usedherein, the term implement refers to a surgical tool or device forperforming medical procedures. An implement could be a drill, a guidewire, or implants such as screws, nails, etc.

Those skilled in the art should recognize that there are many differenttypes of cannulas and many different ways in which cannulas could beused. For example, a cannula could be rigid, semi-rigid, or flexible andcould be configured in any number of different forms, such as acatheter, needle, endoscope, implement inserter, etc.

Utilizing a single cannula means the surgeon typically will positioneach implement individually. The procedure usually starts by attaching areference tracking frame to the surgical anatomy. X-ray images are thentaken utilizing a fluoroscopic imager which is also tracked by thenavigation system. The surgeon then positions the tracked guide for thefirst implement with the aid of the navigational system display. Oncethe tool guide is properly positioned, the cannula is used to place theguide wire and subsequent implement into the desired anatomical site.The next implement is then placed relative to the first, and so on. Inorder for the surgeon to properly place the subsequent implementrelative to the previous, new images are taken with the previousimplement in place.

One difficulty of the current practice is in achieving relative accuracyof the implement placement. To achieve the desired relative implementgeometry, the surgeon estimates each trajectory individually based uponthe prior implements. Thus, the relative accuracy is based on thephysician's estimate. Furthermore, each implement may involve generatinga new set of images of the patient's anatomy before the subsequentimplement can be placed, which can increase the time of the procedureand radiation exposure to both the patient and operating room personnel.

SUMMARY OF THE INVENTION

The present invention is directed generally to image guided medicalprocedures, and, particularly, medical procedures which utilize surgicalimplements. More specifically, the present invention is directed to anapparatus and method for the combined positioning of multipleimplements, especially those that may be placed in a specific relativegeometry.

As embodied and broadly described herein, certain aspects of theinvention are directed to a multiple cannula tool guide for use inconjunction with image-guided surgical navigation systems.

In one aspect of the invention, an apparatus for use in image guidedsurgery is presented. The apparatus comprises: an instrument locationsystem for detecting position, where the instrument location systemincludes a computer processor; a tool guide comprising a plurality ofcannulas; and at least one trackable marker provided on the tool guidefor detection by the instrument location system; a memory coupled to thecomputer processor stores: at least one pre-acquired image of a patienthaving an image space, and instructions, to be executed by the computerprocessor, to align the image space to a detector space, to track athree-dimensional position of the tool guide in, the detector space, andto compute a projection of the tool guide into the at least onepre-acquired image.

In another aspect of the invention, an apparatus for the placement ofsurgical implements is presented. The apparatus comprises: a pluralityof cannulas coupled to a fixture, where at least one trackable markerassociated with the cannulas; a plurality of surgical implementreceivers provided on the fixture for receiving surgical implements; andat least one of the plurality of receivers being substantially coaxiallyaligned with a respective one of the plurality of cannulas.

In another aspect of the invention, an apparatus for the placement ofsurgical implements, is presented. The apparatus comprises: a pluralityof cannulas, where at least one of the plurality of cannulas isadjustable to vary its length; a fixture coupled to the plurality ofcannulas, where the fixture can accommodate at least one of theplurality of cannulas being individually adjustable to vary at least oneof its angular position; and at least one trackable marker associatedwith the cannulas.

In another aspect of the invention, a method for guiding a medicalinstrument for use in image guided surgery is presented. The methodcomprises: providing at least one pre-acquired image of a patient, theat least one image having an image space; aligning the image space and adetector space; tracking a three-dimensional position of a tool guide inthe detector space, using at least one trackable marker provided on thetool guide, where the tool guide includes a plurality of cannulas; andrelating the position of the cannulas with the at least one pre-acquiredimage.

Combined positioning of surgical implements may mitigate the amount ofestimation a surgeon performs when positioning implements individually.This can result in improved placement efficiency and reduced surgicalprocedure time. Additional savings in time may also be realized byreducing the number of pre-acquired images generated during a surgicalprocedure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a simplified block diagram of a system for the combinedpositioning of multiple surgical implements consistent with the presentinvention.

FIG. 2 is a simplified side view of an embodiment of a system for thecombined positioning of multiple surgical implements consistent with thepresent invention.

FIG. 3 is a perspective view of an embodiment of a tool guide consistentwith the present invention.

FIG. 4 is a rear view of the embodiment of the tool guide shown in FIG.2.

FIG. 4 a is a perspective view of another embodiment of a tool guideconsistent with the present invention.

FIG. 4 b is another embodiment of the tool guide having the ability toadjust the relative angles between the cannulas.

FIG. 5 is a block diagram of a process used to place surgical implementsconsistent with the present invention.

FIG. 6 is a simplified block diagram of an exemplary computer systemused in the surgical navigation system in accordance with one embodimentof the invention.

FIG. 7 is an exemplary diagram of a display consistent with anembodiment of the invention showing the trajectory of cannulassuperimposed on images of a patient's anatomy.

DETAILED DESCRIPTION

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

With reference to FIG. 1, there is shown schematically an apparatus inaccordance with the present invention for the combined positioning ofmultiple surgical implements. Image-based surgical navigation system 100enables a surgeon to generate and display on monitor 115 a plurality ofpositions representing each cannula 127 of tool guide 125. Datarepresenting one or more pre-acquired images 105 is fed to navigationcomputer 110. The pre-acquired images, generated prior to implementplacement, typically are taken from different orientations and representthe region of interest of a patient's body which is to receive theimplements. Navigation computer 110 tracks the position of tool guide125 in real time utilizing a detector. The detector may be an sensorarray 120 physically uncoupled from tool guide 125. Alternatively, thedetector could also be at least one trackable marker 121 physicallyattached to or integrated into tool guide 125. Computer 110 thenregisters and displays the position of each cannula 127 with images 105in real time to allow the surgeon to properly position and orient thetool guide into the anatomy for implement placement. The pre-acquiredimages 105 are superimposed on the icons representing each cannula 127on monitor 115. While the present invention described in more detailbelow is exemplified by a fluoroscopic-based system used for femoralneck fracture fixation, it is not limited to the described embodiment.

FIG. 2 illustrates apparatus 125 in use with a preferred image-basedsurgical navigation system 200 according to one embodiment of thepresent invention. System 200, described below in sufficient detail toallow an understanding and appreciation of the present invention, isexplained in greater detail in U.S. patent application Ser. No.09/274,972 of David A. Simon et al., entitled “Navigation Guidance viaComputer Assisted Fluoroscopic Imaging,” filed on Mar. 23, 1999, nowU.S. Pat. No. 6,470,207, issued Oct. 22, 2002, the entire disclosure ofwhich is hereby incorporated by reference. However, it must beunderstood that the invention is not confined to use with thisparticular image guided surgical system.

Further referring to FIG. 2, an image-based surgical navigation system200 for acquiring and displaying x-ray images appropriate for a givensurgical implement procedure is shown. Pre-acquired images of patient202 are collected when a patient, lying on platform 205, is placedwithin C-arm 212 of imaging device 210. The term “pre-acquired,” as usedherein, does not imply any specified time sequence. Pre-acquired imagescould be generated pre-procedurally or intra-procedurally. Preferably,the images are taken before implement positioning is performed.

C-arm 212 may be capable of rotating relative to patient 202, allowingimages of the patient to be taken from multiple directions. For example,the surgeon may rotate C-arm 212 about its mechanical axis as shown byarrows 228. Usually, images are taken from two substantially orthogonaldirections, such as anterior-posterior (A-P) and lateral, of the anatomywhich is to receive the surgical implements. One implementation ofimaging device 210 is the Model 9600 C-arm fluoroscope from OEC MedicalSystems, Inc. of Salt Lake City, Utah.

It is to be understood, however, that the invention is not confined tothe use of a C-arm fluoroscopic device. Other embodiments of theinvention could include imaging systems which produce 3-D volumetricdata. Examples of such 3-D imaging systems include computer tomography,ultrasound, or magnetic resonance imaging. Functional imaging systemssuch as, for example, functional magnetic resonance imaging, positronemission tomography, single photon emission tomography, ormagnetoencephalography, could also be used.

Fluoroscopic images taken by imaging system 210 are transmitted tocomputer 226 where they may be forwarded to surgical navigation computer110. Image transfer may be performed over a standard video connection ora digital link. Computer 110 provides the ability to display, viamonitor 115, as well as save, digitally manipulate, or print a hard copyof the received images. Images, instead of, or in addition to, beingdisplayed on monitor 115, may also be displayed to the surgeon through aheads-up display or some other type of appropriate display device.

Although computers 226 and 110 are shown as two separate computers, theyalternatively could be variously implemented as a single-chassismulti-processor computer or as a single computer that performs thefunctions performed by individual computers 110 and 226. In the singlecomputer case, such computer would directly receive image data fromimage device 210 directly and detector 120.

Further referring to FIG. 2, image-based surgical navigation system 100generally performs the real-time tracking of tool guide 125, and, in theshown embodiment, also tracks the position of C-arm receiver section 216and anatomical reference frame 260. This embodiment utilizes a detectorwhich includes a sensor array 120 which is suspended by mount 250.Sensor array 120 may be located in such a manner as to provide a clearline of sight to the tracking markers on each tracked object (such astracking markers 265, described more fully below). Sensor array 120 iscoupled to computer 110 which may be programmed with software modulesthat analyze the signals transmitted by sensor array 120 to determinethe position of each object in detector space. The manner in which thesensor array localizes the object is known in the art. See also, forexample, PCT Application No. PCT/US95/12894 (Publication No. WO96/11624) to Bucholz, the entire disclosure of which is incorporated byreference.

The tracking markers for each tracked object may be, for example,reflective markers and/or light emitting diodes (LEDs). Other devicesknown in the art may be used that are capable of being tracked by acorresponding detector within the scope of the invention. For purposesof illustration, and not by limitation, the tracking means may beacoustic, magnetic, optical, electromagnetic, inertial, and radiologicaldevices known in the art. It should also be understood that differenttracking markers for each tracked object can be used.

Not all of the tracking devices listed above are used in conjunctionwith sensor array 120. For example, a single electromagnetic trackingmarker is actually a sensor which may be used to provide at least threedegrees of spatial information in detector space. Some electromagneticsensors can also provide additional attitude information, thus providingup to six degrees of positional information. Such sensors may also haveno line of sight constraint which provides the advantage of functioningwhile embedded within a patient. The manner in which electromagneticsensors localize an object is well known in the art. See also, forexample, PCT Application No. PCT/GB93/01736 (Publication No. WO94/04938) to Bladen, the entire disclosure of which is incorporated byreference.

In the embodiment of FIG. 2, anatomical reference frame 260, whichincorporates a plurality of tracking markers 265, is attached to patient202 during an implement procedure. The reference frame may be securelyattached to the anatomy in the region of the body which is to receivethe implements. Reference frame 260 may be placed in a position so thatthe markers are visible to sensor array 120 during the image acquisitionprocess and the implement procedure. By sensing attached trackingmarkers 265, computer 110 can determine the position of the anatomy indetector space. This information is later used by computer 110 toregister pixels found in the images to the position of the patient'sanatomy as described in detector space. For purposes of this document,detector space is defined herein as the three-dimensional referencecoordinate system associated with the detector.

Further referring to FIG. 2, multiple cannula tool guide 125 may betracked by surgical navigation system 100 using attached trackingmarkers 230 in order for its position to be determined in detectorspace. Computer 110 integrates this information with the pre-acquiredimages of patient 202 to produce a display which assists surgeon 270when performing multiple implement procedures. Representations ofmultiple cannulas 127 are overlaid on the pre-acquired images of patient202 and displayed on monitor 115. In this manner, surgeon 270 is able tosee the location of the cannulas relative to the patient's anatomy, andcan position and orient multiple implements into the desired portion ofpatient's body.

Image-based surgical navigation system 100 utilized in the embodiment ofthe invention shown in FIG. 2 may be the same as that used in theFluoroNav™ system, which utilizes the StealthStation® Treatment GuidancePlatform, both of which are available from Medtronic Sofamor Danek, Inc.

FIG. 3 is a perspective drawing of an embodiment of tool guide 125 whichis optimized for the combined positioning of cannulated screws to securefemoral neck fractures. A plurality of tracking markers 230 arepositioned at points on the upper surface of frame 300. Frame 300 firmlyattaches to a body 305 of tool guide 125 by sliding onto a dovetailformed on the top of mounting post 380. Frame 300 may be interchangedwith other frames which utilize different sizes or shapes, or trackingmarkers of a different type. In the embodiment shown in FIG. 3, trackingmarkers 230 may be infrared LEDs and/or reflective markers such as thosesupplied by Northern Digital Inc.

For the embodiment shown in FIG. 3, tool guide 125 includes threesubstantially parallel cannulas 310 a, 310 b, 310 c. Cannula 310 a has afixed length and the other cannulas 310 b, 310 c have lengths which arevariable. However, in general, the invention could comprise a tool guidewhere all the cannulas, or any subset thereof, may have variablelengths. The variable length cannulas can be independently adjusted bythe use of threaded means 330, which screw into interchangeable fixture350 and are locked in place using a set screw or jam nut (not shown).Variable length cannulas allow tool guide 125 to adapt to the varyingsurface shapes associated with different bone structures. The surgeon,using information from the pre-acquired images, can make the properlength adjustment to each adjustable cannula during the pre-operativeplanning stage of the medical procedure. The cannulas may possess teeth360 a, 360 b, 360 c at their distal end in order to effectively grip thepatient's bone.

Furthermore, tool guide 125 may have cannulas which have inner and outerdiameters that are also variable. These diameters may be altered bysimply interchanging a given cannula with another having differingdiameters, or alternatively, using cylindrical adapters to modify thediameters of an existing cannula. For example, the inner diameter of thelumen may be reduced by inserting a reduction sleeve which extends thelength of the cannula. Various reductions in lumen diameter can beachieved through the insertion of one or more reduction sleeves.Alternatively, the outer diameter of a cannula may be increased in asimilar manner by sliding one or more expansion sleeves over the outsideof the cannula. Other embodiments of tool guides can be provided bychanging fixture 350. For example, one such interchangeable fixture 350could have cannulas with non-parallel, fixed angular offsets. In theembodiment of FIG. 3, cannulas 310 b and 310 c can be removed byunscrewing them from fixture 350. The fixture may then be slid offcannula 310 a and replaced with another having differentcharacteristics. For example, the number of cannulas can be varied byutilizing fixtures which have a different number of attachment points.Additionally, the relative geometry, or spread, between the cannulas canbe varied by utilizing fixtures which have attachment points indifferent relative locations. Finally, the relative angulations amongthe cannulas may be altered from a parallel configuration by employing afixture having attachment points with fixed angular offsets.

Many different types of cannulas could be used with the invention in itsbroadest aspects. In the embodiment shown in FIG. 3, the cannulas 360 a,360 b, 360 c are preferably substantially rigid tubular members eachhaving a lumen extending therethrough that is configured to allow forpassage of surgical implements, such as drills or other tools, and/ordevices, such as cannulated screws, nails, etc.

The surgeon typically holds and manipulates tool guide 125 by graspinghandle 340 shown in FIG. 3. Alternatively, the invention could also bephysically manipulated by a machine, such as, for example, a roboticarm. Machine manipulation could be facilitated through a coupling onbody 305 which could allow tool guide 125 to be removably attached to amechanized placement system. This arrangement could facilitate highlyaccurate placement of surgical implements, without usage of handle 340.

FIG. 4 is a rear-view perspective drawing of the embodiment of toolguide 125 shown in FIG. 3. Situated towards the proximal end of the eachcannula is a flange 370, attached to body 305. At the flange center is acountersunk hole 375 which leads to the lumen of the cannula. Flange 370and hole 375 is a surgical implement receiver which assists the surgeonin the placement of implements down the cannulas once tool guide 125 isproperly positioned in the patient's body. For a procedure, for example,to secure a femoral neck fracture, a drill with an attached guide wireis sequentially placed down each cannula after tool guide 125 has beenappropriately positioned relative to the patient's body. The surgeondrills into the bone in order to anchor the guide wire. A cannulatedscrew is then placed over each guide wire and the screw is tapped intothe bone at the fracture site. Once the screws are in place and secured,the guide wires are removed along with tool guide 125.

FIG. 4 a shows an embodiment of a tool guide having electromagneticsensors attached to cannulas 310 a, 310 b, and 310 c. Electromagneticsensors may be placed at the approximate mid-point of each cannula, asshown by 315 a, 315 b, and 315 c, and/or they may be placed towards thetips of each cannula as shown by 317 a, 317 b, and 317 c.Electromagnetic sensor groups 315 a-c and 317 a-c may be used separatelyor in conjunction with each other. Utilizing both groups can allow forthe extraction of trajectory information of each cannula. Typically,each cannula would be equipped with separate electromagnetic sensors,however; some embodiments may have just one, or any subset of the totalnumber of cannulas, equipped with electromagnetic sensors.

FIG. 4 b exemplifies another embodiment of a tool guide having cannulaswith adjustable relative angles. Cannulas 401 and 402 are set in fixture405 such that the base of each cannula can pivot within the fixture. Theangle of each cannula can be varied independently in the azimuth,.theta., 412 and elevation, .phi., 414 directions relative to fixture405. After the angles for each cannula have been adjusted as desired,mechanism 410 can lock each cannula in place. Mechanism 410 can be afriction or compression lock, or any other type of locking mechanismknown in the art. The orientation of cannulas 401, 402 shown as mutuallyparallel in FIG. 4 b is only for purposes of explanation, and notlimitation. Other embodiments which allow the cannulas to have a varyingangular position which are known in the art could be used. It shouldalso be understood that the tool guide shown in FIG. 4 b could have anynumber of cannulas, and in addition to each angle being variable, eachcannula could be individually adjusted in length.

FIG. 5 is a flowchart illustrating methods for multiple implementpositioning using image-based surgical navigation techniques. Thesurgeon may begin by acquiring one or more images of a patient. In oneembodiment, these may be acquired with fluoroscopic x-ray imager 210, asshown in system of FIG. 2. Alternatively, such images may be acquiredwith an imaging device with provides 3-D volumetric data (step 510).

Computer 110 then retrieves a pre-acquired image and correlates thespatial coordinates defined by the images, known as image space, withthe spatial coordinates defined by the detector, known as detectorspace. As shown in the embodiment of FIG. 2, computer 110 may retrieve apre-acquired image from C-arm control computer 226. Computer 110 thendetermines location information of receiver section 216, and anatomicalreference frame markers 265, using sensor array 120. Computer 110 thencorrelates the images to anatomical reference marker 260, by determiningand applying a geometric transform well known to those skilled in theart. Computer 110 then stores the image along with its positionalinformation (step 520). The processes described in step 520 are repeatedfor each image to be acquired.

The implement placement procedure starts once a detector and computer110 detect and track the position of tool guide 125 relative to patient202 in detector space. With this information, computer 110 dynamicallycalculates, in real time, the projections of cannulas 127 into eachimage as tool guide 125 is moved by surgeon 270. Typically, the surgeonplaces the cannulas into the patient percutaneously into the region ofinterest to position the implements (step 530). However, the inventioncan be used with other surgical techniques.

Graphical representations of cannulas are superimposed on pre-acquiredimages and displayed on monitor 115. The cannulas can be displayed,simultaneously if desired, and in real time relative to the patient'sanatomy (step 540). The surgeon, utilizing the display, can thenmanipulate tool guide 125 and position cannulas 127 in the region ofinterest. Using real-time display 115, the physician gets feedback onhow the cannulas are oriented relative to the anatomy and thendetermines the optimal orientation (step 550). Once this is determined,the surgeon will then sequentially place the implements into thepatient. If, for example, the procedure involves the fixation of afemoral neck fracture as previously described, the surgeon first placesa drill with an attached guide wire down the cannula to drill into thebone at the fracture site and then anchor the guide wire into the bone.The surgeon then places a cannulated screw over the guide wire and downinto the cannula. The screw taps into the bone at the fracture site andpulls the separate pieces of bone together. This process is repeated foreach cannulated screw while the surgeon steadily holds tool guide 125 inplace. Alternatively, the surgeon may place the guide wires using thecannulas and then remove the guide from patient's body. The surgeonwould then position the screws by placing them over each guide wire,leading them to the bone into the fracture site (step 560).

Referring to FIG. 6, components and modules of a computer system 110used to perform various processes of the present invention aredescribed. Although a STEALTH STATION® image guided system manufacturedby Medtronic Sofamor Danek has been identified, it will be appreciatedthat the present invention may be utilized with other types of computersystems. One aspect of the computer system 110 includes a graphical userinterface system operating in conjunction with a display screen of adisplay monitor 115. The graphical user interface system is preferablyimplemented in conjunction with operating system 615 running computer110 for displaying and managing the display objects of the system. Thegraphical user interface is implemented as part of the computer system110 to receive input data and commands from a conventional keyboard 620and mouse 625. For simplicity of the drawings and explanation, manycomponents of a conventional computer system have not been illustratedsuch as address buffers, memory buffers, and other standard controlcircuits because these elements are well known in the art and a detaileddescription thereof is not necessary for understanding the presentinvention. A computer program used to implement the various steps of thepresent invention is generally located in memory unit 600, and theprocesses of the present invention are carried out through the use of acentral processing unit (CPU) 605. Those skilled in the art willappreciate that the memory unit 600 is representative of both read-onlymemory and random access memory. The memory unit also includes adatabase 650 that stores data, for example, image data and tables,including such information as position data and geometric transformparameters, used in conjunction with the present invention. CPU 605, incombination with the computer software comprising operating system 615,detection software module 630, tracking software module 635, calibrationsoftware module 640, and display software module 645, controls theoperations and processes of computer system 110. The processesimplemented by CPU 605 may be communicated as electrical signals alongbus 660 to an I/O interface 670 and a video interface 675.

Detection software module 630 utilizes signals from the detector andperforms the processes associated with creating a coordinate referencesystem and detecting positions of reference images for use in connectionwith the present invention and are known to those skilled in the art.Tracking software module 635 performs the processes necessary fortracking objects in an image guided system as described herein and areknown to those skilled in the art. Correlation software module 640computes the geometric transform which registers the images to thedetector space, and thus the patient's anatomy.

Display software module 645 applies, and if necessary, computes theoffsets between tool guide tracking markers 230 and the cannulas inorder generate an icon representing each cannula for superposition overthe images. For tool guides with fixed cannulas, these offsets can bemeasured once and stored in database 650. The user would then selectfrom a list of tool guides which one was being used in the procedure sothe proper offsets are applied by display software module 645. For toolguides with variable lengths and angulations, the offsets could bemeasured manually and entered via keyboard 620, or measured using thenavigation system 100 in conjunction a tracked pointer or trackedregistration jig (not shown). If a tracked pointer is used, the userwill touch the tip and tail of each cannula while the tool guide isbeing tracked. The offsets are computed by display software module 645and stored for later use. Similarly, if a tracked registration jig isused, the tool guide is placed within the jig while it is being tracked.The jig will measure the positions of the cannulas and display softwaremodule 645 will again compute the offsets and store them for later usein database 650.

Pre-acquired image data 105 can be fed directly into computer 110digitally through I/O interface 670, or may be supplied as video datathrough video interface 675. In addition, items shown as stored inmemory can also be stored, at least partially, on hard disk 680 ifmemory resources are limited. Furthermore, while not explicitly shown,image data may also be supplied over a network, through a mass storagedevice such as a hard drive, optical disks, tape drives, or any othertype of data transfer and storage devices which are known in the art.

FIG. 7 shows an exemplary diagram of display 700 illustrating an iconicgraphical overlay of the cannulas for the preferred embodiment. Display700 is presented to the surgeon on monitor 115 of computer system 110.The left side of FIG. 7 shows a fluoroscopic image of ananterior-posterior view of a hip and femoral neck bone 710. Graphicaloverlays 715 are the iconic superposition of all the cannulas 127attached to tool guide 125 within image 710. Graphical overlays 715 aredirectional indicators, displaying the position and orientation of eachcannula. In the embodiment shown in FIG. 7, these directional indicatorsare shown as lines, but other symbols may be used. As the surgeon movestool guide 125, computer 110 recalculates and displays the new locationsof the graphical overlays 715. The surgeon can use image 710 andoverlays 715 to visualize, in real-time, the position and orientation ofthe cannulas relative to the patient's anatomy.

For the embodiment shown in FIG. 2, the surgeon would like to acquiretwo substantially orthogonal fluoroscopic images of patient 202, such asimages from an anterior-posterior view and a lateral view of the anatomyof interest. These two complementary views help the surgeon to bettervisualize how the cannulas are situated in the patient's anatomy. Theorthogonal views are related to one another by a 90 degree rotationabout the major axis of the patient (the axis running along the lengthof the patients body). The fluoroscopic image taken from the lateralview 720 is shown on the right side of FIG. 7, along with graphicaloverlays 717 showing the locations of the cannulas 127.

In certain situations, the surgeon may wish to know where the tip of thecannulas would be if cannulas were projected along a line give by a toolguide's current trajectory. At the surgeon's command, computer 110 maycalculate and display this projection based upon the current orientationand position of the cannulas. This orientation and position aredetermined by tracking the tip and the tail of each cannula. Theestimated position of the tip can be calculated by computer 110 throughprojecting a fixed distance beyond the cannulas' tips in the directionof the line formed by each cannula's tip and tail. The estimatedposition, or “look-ahead” trajectory, would be represented by agraphical overlay. As shown in FIG. 7, exemplary “look-ahead”trajectories 725 and 727 are shown in a different line styles fromoverlay 715 and 717, respectively. This difference could also be achange in color, type, or texture between the look-ahead trajectory 725,727 and the current position 715, 717. Computer 110 may vary the lengthof the look-ahead trajectory 725, 727 as directed by the surgeon throughthe graphical user interface control 730 and computer keyboard 620 ormouse 625. In this manner, computer 110 assists the surgeon invisualizing where the cannulas would be in the patient if they wereadvanced a predetermined distance into the body of the patient.

Although the look-ahead technique described above projected thegraphical representation of the cannulas into the image, there is norequirement that the cannulas' graphical representation be in the spaceof the image for look ahead trajectory 725, 727 to be projected into theimage. In other words, for example, the surgeon may be holding toolguide 125 above the patient and outside the space of the image, so thatthe representation of the cannulas does not appear in the images.However, it may still be desirable to project ahead portion 725, 727into the image to facilitate planning of the implement procedure.

The look-ahead technique could be extended to include virtual implants.Graphical overlays representing implant structures such as prostheticdevices, plates, and fasteners such as screws, nails, etc., could beshown on display 115 during and after their placement into the patient'sbody. These graphical overlays would provide additional informationregarding the implants without involving the generation of new images.

When cannulas 127 are perpendicular to the plane of the fluoroscopicimage, the graphical overlay of the cannulas may virtually collapse to apoint, potentially making it difficult to view them. To alleviate this,computer 110 may optionally use a different graphical representation ofcannulas 172 when the distance in the image plane between the tip andtail of the cannulas 127 becomes smaller than some fixed distance.

The foregoing description is presented for purposes of illustration andexplanation. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and modifications of variationsare possible in light of the above teachings or may be acquired frompractice of the invention. The principles of the invention and itspractical application enable one skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated.

For example, pre-acquired images obtained from modalities different thanthe C-arm fluoroscope x-ray imager may be used with the invention. Suchmodalities could supply 3-D volumetric data and may also includefunctional information. Such modalities may include, by way of exampleonly, computer tomography, ultrasound, or magnetic resonance imaging.Imaging modalities which may provide functional information includefunctional magnetic resonance imaging, positron emission tomography,single photon emission tomography, magnetoencephalography, or any othermodality known to those skilled in the art.

Furthermore, the invention is not limited to the fixture of femoral neckfractures, but can be used for many different types of procedures suchas the distal locking of intramedullary nails, in placing implementssuch as interbody fusion devices into the spine, anterior cervicalplating systems, etc., or any other application where two or moreimplements are to be placed, especially multiple implements having fixedrelative positions and angulations.

1. An apparatus for the placement of surgical implements, comprising: afixture that defines a plurality of attachment points that are spacedapart and fixed relative to each other; a plurality of cannulas coupledto the fixture with each of the plurality of cannulas coupled to arespective one of the plurality of attachment points; at least onetrackable marker mounted on a frame that is coupled to the fixture toenable an instrument location system to detect a position of each of theplurality of cannulas throughout a surgical procedure withoutobstructing any of the cannulas during the procedure; and a plurality ofsurgical implement receivers provided on the fixture for receivingsurgical implements, at least one of the plurality of receivers beingsubstantially coaxially aligned with a respective one of the pluralityof cannulas to enable a surgical implement to pass through a respectiveone of the plurality of receivers and a respective one of the pluralityof cannulas.
 2. The apparatus of claim 1, further comprising: aperipheral structure, coupled to the fixture to move the fixture andthereby maneuver the plurality of cannulas during a surgical procedureto place the surgical implements.
 3. The apparatus of claim 2, whereinat least one of the surgical receivers is a flange configured to receivethe surgical implements.
 4. The apparatus of claim 2, wherein at leastone of the plurality of cannulas is individually adjustable to vary itslength.
 5. The apparatus of claim 2, wherein at least one of theplurality of cannulas is individually adjustable to vary an angularposition of at least one of the plurality of cannulas relative to thefixture and the peripheral structure.
 6. The apparatus of claim 5,wherein the at least one angular position is an azimuth angular positionmeasured in a horizontal reference plane associated with the fixture. 7.The apparatus of claim 5, wherein the at least one angular position isan elevation angular position measured in a vertical reference planeassociated with the fixture.
 8. The apparatus of claim 2, wherein thefixture is interchangeable from the peripheral structure, and whereinthe fixture is configured to accommodate at least one of: a variablenumber of cannulas, cannulas having a plurality of relative placements,or cannulas having a plurality of fixed relative angles.
 9. Theapparatus of claim 2, wherein the peripheral structure is a pistol gripconfigured graspable handle.
 10. The apparatus of claim 2, wherein theperipheral structure is machine operated.
 11. The apparatus of claim 2,further comprising: a plurality of interchangeable frames, at least twoof the frames having a different type of trackable marker.
 12. Theapparatus of claim 2, wherein the surgical implement is at least one ofa surgical tool or an implant.
 13. The apparatus of claim 2, wherein atleast one of the plurality of cannulas can be interchanged with acannula having at least one of a different inner diameter or outerdiameter.
 14. The apparatus of claim 2, wherein at least one of theplurality of cannulas is individually adjustable to vary at least one ofits inner diameter or outer diameter.
 15. The apparatus of claim 2,wherein at least one of the plurality of cannulas includes a serratedstructure for gripping portions of a patient's anatomy.
 16. Theapparatus of claim 2, wherein the at least one trackable marker isselected from a group comprising a reflective marker, a light emittingmarker, an acoustic marker, a magnetic marker, an optical marker, anelectromagnetic marker, a radiological marker, and combinations thereof.17. The apparatus of claim 2, wherein the frame is removably coupledrelative to the fixture using a dove-tail connection, wherein thedove-tail connection further comprises: a dovetail connection memberhaving a first planar surface and a second planar surface, wherein thefirst planar surface and the second planar surface are positioned at anacute angle relative to one another; and a riser member extending alength and interconnecting the dove-tail connection member and thefixture, to position the dovetail connection member a distance from thefixture.
 18. The apparatus of claim 2, wherein the peripheral structureis fixed relative to the plurality of attachment points.
 19. Theapparatus of claim 1, further comprising: a display that displays anicon representative of the position of each of the plurality of cannulasoverlaid onto an image of the anatomy.
 20. A kit for an apparatus forthe placement of surgical implements, comprising: a first fixture havinga first configuration defined by a plurality of attachment points thatare spaced apart and fixed relative to each other and a first framecoupling region; a second fixture different from the first fixture andhaving a second configuration defined by a plurality of attachmentpoints that are spaced apart and fixed relative to each other and asecond frame coupling region; a plurality of cannulas each operable tobe coupled to at least one of the first fixture or the second fixturevia one of the respective plurality of attachment points; and atrackable marker operable to be associated with all of the plurality ofcannulas, the trackable marker mounted on a single frame, the singleframe operable to be selectively coupled to the first frame couplingregion of the first fixture or the second frame coupling region of thesecond fixture, wherein upon coupling the plurality of cannulas with thefirst fixture or the second fixture, the plurality of cannulas arepositioned in at least one of the first configuration or the secondconfiguration, and the trackable marker is detectable by an instrumentlocation system to detect the position of the plurality of cannulasrelative to an anatomy in real-time.
 21. The apparatus of claim 20,wherein the plurality of cannulas are positioned parallel to one anotherin the first configuration.
 22. The apparatus of claim 21, wherein thesecond fixture is operable to enable at least one of the plurality ofcannulas to be individually adjustable to vary its angular positionrelative to the second fixture.
 23. The apparatus of claim 20, whereinat least one of the plurality of cannulas is individually adjustable tovary its length.
 24. The apparatus of claim 20, wherein at least one ofthe plurality of cannulas is individually adjustable to vary at leastone of its angular positions.
 25. The apparatus of claim 20 wherein thefirst frame coupling region and the second frame coupling region aresubstantially similar and operable to both couple with the single frameindividually and separately.
 26. The apparatus of claim 25, wherein thetrackable marker is selected from a group comprising a reflectivemarker, a light emitting marker, an acoustic marker, a magnetic marker,an optical marker, an electromagnetic marker, a radiological marker, andcombinations thereof.
 27. The apparatus of claim 25, wherein thesurgical implement is at least one of a surgical tool or an implant. 28.The apparatus of claim 25, further comprising: a plurality ofinterchangeable single frames, at least two of the frames having adifferent type of trackable marker.
 29. The apparatus of claim 25wherein the first frame coupling region and the second frame couplingregion both further comprise: a dovetail connection member having afirst planar surface and a second planar surface, wherein the firstplanar surface and the second planar surface are positioned at an acuteangle to one another; and a riser member extending a length andinterconnecting the dovetail connection member and the fixture, toposition the dovetail connection member a distance from the fixture. 30.An apparatus for the placement of surgical implements, comprising: afixture that includes a pistol grip configured grasping handle and aplurality of attachment points that are spaced apart and fixed relativeto each other; a plurality of cannulas each coupled to a respective oneof the plurality of attachment points of the fixture so thatmanipulation of the pistol grip configured grasping handle maneuvers theplurality of cannulas simultaneously and the plurality of cannulas areindependently adjustable relative to the fixture; a plurality oftrackable markers coupled to the fixture; a surgical navigation systemthat tracks the plurality of trackable markers to determine a positionof each of the plurality of cannulas relative to an anatomy; and adisplay that displays an icon representative of the position of each ofthe plurality of cannulas superimposed onto an image of the anatomy. 31.The apparatus of claim 30, further comprising: a plurality of surgicalimplement receivers provided on the fixture for receiving surgicalimplements, at least one of the plurality of receivers beingsubstantially coaxially aligned with a respective one of the pluralityof cannulas.
 32. The apparatus of claim 31, further comprising: animaging device operable to acquire one or more images of the anatomy.33. The apparatus of claim 30, wherein the fixture is interchangeableand is configured to accommodate at least one of: a variable number ofcannulas, a plurality of cannulas having a plurality of placementsrelative to the fixture, or a plurality of cannulas having a pluralityof fixed relative angles.
 34. The apparatus of claim 33, wherein thepistol grip configured grasping handle includes an elongated memberoperable to be grasped by a hand of a user; wherein the elongated memberextends at an angle of less than 180 degrees relative to a long axis ofany of the plurality of the cannulas coupled to the fixture.
 35. Theapparatus of claim 30, wherein the display also displays a plurality oficons that each represent a projected trajectory for each of theplurality of cannulas superimposed onto the image of the anatomy.